U.S. Postal Service letter carrier Juan Padilla arranges mail in his truck while on his delivery route in San Francisco in 2011. / Justin Sullivan, Getty Images

by Gary Strauss, USA TODAY

by Gary Strauss, USA TODAY

First, it was doing away with Saturday delivery. Now, door-to-door service could be coming to an end.

In an effort designed to cut costs at the cash-strapped agency by up to $4.5 billion a year, congressman Darrell Issa, R-Calif., is proposing that the U.S. Postal Service phase out door-to-door delivery and shift service curbside and to neighborhood cluster boxes.

The proposal - due for vote by the House Oversight and Government Reform Committee on Wednesday - would affect about 37 million residences and businesses.

The Postal Service spends about $30 billion annually on mail delivery, losing $15.9 billion last year alone. It does not receive federal assistance, getting revenue from postage sales, delivery services and other products. But mail service has dropped nearly 25% from 215 billion pieces delivered in 2006 to a current volume of 160 billion, says Postal Service spokeswoman Sue Brennan.

The Postmaster General's office estimates labor-intensive door-to-door delivery costs an average $353 a year. Curbside delivery averages $224; cluster boxes, just $160. The Postal Service, currently making 54 million curbside deliveries and 40 million to cluster boxes and central locations, has been moving toward collective deliveries at shopping malls, business parks and newer residential developments.

"A balanced approach to saving the Postal Service means allowing USPS to adapt to America's changing use of mail,'' Issa said in a statement. "Done right, these reforms can improve the customer experience through a more efficient Postal Service."

Postmaster General Patrick Donahoe has been seeking flexibility in the way the Postal Service delivers mail, such as cutting Saturday delivery - which drew strong public and congressional criticism when it was proposed last year. In April, the Postal Service said it was scuttling plans to end Saturday service this summer, although ending six-day service is still eventually possible, says Ali Ahmad, communications adviser to the Oversight and Government Reform Committee, which Issa chairs.

The National Letter Carriers Association, which opposes ending six-day delivery, is also against ending door-to-door delivery, which is says would hurt jobs and harm elderly and shut-ins who would have difficulty receiving mail.